1. Field of the Invention
The present invention relates to data storage apparatus for magnetically reading and writing information on data storage media. More particularly, the invention concerns the fabrication of suspension assemblies designed to carry read/write heads in magnetic disk drive storage devices.
2. Description of the Prior Art
By way of background, a read/write head in a magnetic disk drive storage device (xe2x80x9cdisk drivexe2x80x9d) is typically incorporated on an air bearing slider that is designed to fly closely above the surface of a spinning magnetic disk medium during drive operation. The slider is mounted to the free end of a suspension that in turn is cantilevered from the arm of a pivotable actuator. When energized, the actuator sweeps the actuator arm and the cantilevered suspension across the disk surface, allowing the read/write head to read and write data in a series of concentric tracks.
The suspension of a conventional disk drive typically includes a relatively stiff load beam whose base end (known as the xe2x80x9cmount platexe2x80x9d) is attached to the actuator arm and whose free end (known as the xe2x80x9cfunctional endxe2x80x9d) mounts a flexure that carries the slider and its read/write head. Disposed between the mount plate and the functional end of the load beam is a xe2x80x9chingexe2x80x9d that is compliant in the vertical bending direction (normal to the disk surface). The hinge enables the load beam to suspend and load the slider and the read/write head toward the spinning disk surface. It is then the job of the flexure to provide a gimbaled support for the slider so that the read/write head can pitch and roll in order to adjust its orientation for unavoidable disk surface run out or flatness variations.
The foregoing suspension components are quite small. A typical suspension is about 18 mm in length. The load beam typically has a thickness of between about 0.03-0.1 mm and the flexure typically has a thickness of between about 0.02-0.03 mm. The slider is typically about 1.25 mm long x 1.00 mm wide x 0.30 mm thick, and the read/write head carried thereon is a fraction of that size.
A design requirement of a disk drive suspension is that it be sufficiently compliant in the vertical bending direction to facilitate proper gram loading of the slider and the read/write head relative to the supportive air bearing force. At the same time, the suspension must be relatively stiff in the horizontal direction (parallel to the disk surface) to prevent off-track sway misalignment. It must also be torsionally stiff to prevent off-track rotational misalignment. In addition to these static structural requirements, the suspension must have good dynamic characteristics to prevent unwanted vibration and flutter. Excessive gain caused by resonance at critical dynamic frequencies can induce unwanted torsion, sway and bending displacements, all of which can contribute to track misalignment problems, excessive noise, and undue wear. Dynamic design considerations have become particularly acute as TPI (Tracks Per Inch) recording density requirements continue to increase. This has necessitated higher track servoing bandwidths, which in turn has established a need for higher dynamic performance suspensions.
Historically, disk drive suspensions have been fabricated using welding processes. In some load beam designs, for example, a single sheet of stainless steel has stainless steel pieces welded to it to develop the required thicknesses for the mount plate and the functional end. The hinge is defined by the initial sheet material that lies between the welded pieces. In other load beam designs, the mount plate, the hinge and the functional end are assembled from three different pieces of stainless steel sheet stock that are welded together. The flexure portion of the suspension also entails welding. In particular, welds are normally used to attach the flexure to the load beam.
A disadvantage of welded suspension designs is that welding requires an additional processing cycle that includes fixturing and multiple processing steps. Welding can also introduce thermal distortions at the weld points. This leads to flatness variations relative to the principal plane of the component parts. Flatness is an important parameter to control because a non-flat suspension can cause suspension flutter due to air flow at operational disk rotation speeds. Welding also tends to reduce the real estate available for components such as piezoelectric milliactuators or the like. There are also free vibrating lengths of material between the weld points that contribute to dynamic flutter and mode gains at critical frequencies, thereby adversely affecting performance. Fixturing will introduce additional alignment tolerance.
Accordingly, there is a need for improvement in the design and manufacture of disk drive suspensions. What would be particularly desirable is a suspension that is substantially, if not completely, weld free in its construction.
The foregoing problems are solved and an advance in the art is obtained by an improved method of manufacturing a suspension designed to carry a read/write head in a data storage device. According to preferred implementations of the invention, a weld free suspension is formed from a composite laminate structure that includes a first, second, third, fourth and fifth material layers. The layers are arranged such that the second layer is disposed between the first and third layers, and the fourth layer is disposed between the third and fifth layers.
The laminate structure is configured using a suitable removal process, such as chemical etching, to define a mount plate, a hinge, a load beam functional end, and an electrical lead system. The mount plate preferably comprises at least the first, second and third layers, and may also include the fourth and fifth layers. The load beam functional end preferably comprises at least the third, fourth and fifth layers, and may also include the first and second layers. The hinge represents an area between the mount plate and the load beam that can be defined by removing all or part of the first and second layers. The electrical lead system is preferably defined by first portions of the fifth layer that are created by removing second portions of the fifth layer.
The laminate structure can be further formed with a flexure gimbal system that comprises only the third, fourth and fifth layers. The flexure gimbal system may include a slider attachment area and gimbaling flexure members formed from the third layer.
A variety of materials can be used to form the layers of the laminate structure. For example, the first layer can be made from a material selected from the group consisting of structural load bearing materials, including but not limited to stainless steel, copper, and glass/ceramic materials. The second layer can be made from a material selected from the group consisting of electrically insulating materials, electrically conductive materials and damping materials, including but not limited to polyimides, copper, aluminum, and viscoelastic polymers. The third layer can be made from a material selected from the group consisting of structural load bearing materials, including but not limited to stainless steel and copper. The fourth layer can be made from a material selected from the group consisting of electrically insulating materials and damping materials, including but not limited to polyimides and viscoelastic polymers. The fifth layer can be made form a material selected from the group consisting of electrically conducting materials, such as copper.
The invention further contemplates a suspension assembly comprising a suspension constructed according to the inventive method in combination with a transducer-carrying slider, and a disk drive incorporating the suspension assembly.